Canada's goal of admitting 50,000 Syrian refugees by year's end is provoking security concerns in Washington, where lawmakers Wednesday questioned Ottawa's ability to adequately screen a large influx of newcomers on a short timetable.

Given the porous U.S.-Canadian border, any terrorist infiltrators admitted to Canada could easily slip into the United States, according to the chairman of the Senate Homeland Security Committee, Republican Ron Johnson.

"We have a pretty unsecured border with Canada. It's never represented much of a threat," Johnson said. "Islamic terror represents a threat. It's real, it's growing. This is a legitimate concern."

The senator represents Wisconsin, which shares Lake Superior with Canada. He presided over a hearing Wednesday in which Canadian experts testified about the challenges posed by newly-installed Prime Minister Justin Trudeau's pledge to accept 25,000 Syrian refugees by March 1, and a total of 50,000 by December.

Monumental task

Canadian intelligence expert David Harris said the task before Canada is monumental, given that the United States has only agreed to admit 10,000 Syrians and the U.S. population is nine times that of Canada.

FILE - Canada's Prime Minister Justin Trudeau helps a young Syrian refugee try on a winter coat after she arrived with her family from Beirut at the Toronto Pearson International Airport in Mississauga, Ontario, Canada, Dec. 11, 2015.

"Therefore, 25,000 refugees in Canada would be the equivalent of 225,000 refugees in the United States," Harris said. "If the extensive U.S. intelligence system would have trouble security-screening 10,000 Syrians in a year, how likely is it that Canada, even with valuable U.S. assistance, could adequately screen two-and-a-half times that number in four months?"

In advance of the hearing, Canada's ambassador in Washington, Gary Doer, wrote the committee, saying, "Rest assured that no corners, including security screening, are being cut in order to achieve the government's objectives. Rather, the government has devoted significant resources to this effort."

Canadian immigration attorney Guidy Mamann told senators that Canadian agencies involved in refugee matters will do their utmost to fulfill their duties.

"I have no doubt that they will not intentionally cut corners in order to deliver a politically expedient result," Mamann said. "However, they will be under tremendous pressure to deliver an unprecedented volume of work in record time. … They are going to be tired."

Opposition called irrational

A Republican-led effort to impose strict conditions on the acceptance of Syrian refugees to the United States passed in the House of Representatives but failed in the Senate last month. More than two dozen governors have said they do not want Syrians settled in their states.

Whether in the United States or Canada, fear of Syrian refugees is irrational, according to Sen. Tom Carper, the committee's top Democrat, who noted there are far quicker and easier routes to get to North America.

"An ISIS person would have to be crazy or stupid to try to get here through our most-closely vetted program," Carper said, using an acronym for Islamic State. "From what I can tell, it [Canada's refugee program] looks a lot like ours. Like us, Canada carefully screens potential candidates while they are overseas."

The committee also received testimony from U.S. Border Patrol agent Dean Mandel, who said the U.S.-Canadian border is not difficult to traverse legally or illegally. Even so, Mandel noted that refugees account for a tiny proportion of the foreigners arriving in Canada, including tourists, students and business travelers.

"Candidly, of greater concern [than Syrian refugees] for me, from a border security perspective, are over 5 million foreign visitors that enter Canada annually," Mandel said.